Field of the Invention
The present invention relates to a method of manufacturing a photoelectric conversion device.
Description of the Related Art
In a semiconductor device manufacturing process, annealing can be performed in a hydrogen-containing atmosphere in order to terminate a dangling bond at the interface between a semiconductor substrate and an insulating film thereon. Japanese Patent No. 3149169 has described a technique of performing annealing at 450° C. in a 3%H2 Ar atmosphere after forming the first protective insulating film (silicon oxide film) on a metal wiring and forming the second protective insulating film (silicon nitride film) on the first protective insulating film at 370° C. Note that Japanese Patent No. 3149169 is not directed to the manufacture of a photoelectric conversion device or a solid-state image sensor.
In a field of a photoelectric conversion device such as a CMOS image sensor or a CCD image sensor, various efforts are being made to reduce a dark output (dark current). The dark output is a signal generated even though the photoelectric conversion device is not exposed to light.
As a method of reducing the dark output, for example, a method of forming a silicon nitride film after forming an electrically conductive pattern, and then performing annealing in a hydrogen-containing atmosphere is considered. When such annealing is performed, however, a lost part (void) may be formed in the electrically conductive pattern in the annealing.
Occurrence of a lost part will be described with reference to FIG. 8. Note that FIG. 8 is a view created by the present applicant in order to describe the lost part that may be formed by annealing and does not form the prior art. A wiring structure 400 includes a silicon oxide film 410, an electrically conductive pattern 420 arranged on the silicon oxide film 410, a silicon oxide film 430 arranged so as to cover the electrically conductive pattern 420, and a silicon nitride film 440 arranged on the silicon oxide film 430. The electrically conductive pattern 420 can have a stacked structure of a barrier metal 421, a metal layer 422 containing aluminum, and a barrier metal 423. A lost part 450 can be formed by executing annealing in a hydrogen-containing atmosphere after the silicon nitride film 440 is formed. A cause of this has not been clarified yet. However, movement of aluminum making up the metal layer 422 in a process of reducing the stress of the electrically conductive pattern 420 in annealing is considered as a possibility of that cause.